Just what is a thyristor?

A thyristor is actually a high-power semiconductor device, also referred to as a silicon-controlled rectifier. Its structure includes 4 quantities of semiconductor elements, including 3 PN junctions corresponding for the Anode, Cathode, and control electrode Gate. These 3 poles are definitely the critical parts from the thyristor, allowing it to control current and perform high-frequency switching operations. Thyristors can operate under high voltage and high current conditions, and external signals can maintain their working status. Therefore, thyristors are commonly used in a variety of electronic circuits, such as controllable rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversion.

The graphical symbol of any Thyristor is normally represented from the text symbol “V” or “VT” (in older standards, the letters “SCR”). Additionally, derivatives of thyristors also have fast thyristors, bidirectional thyristors, reverse conduction thyristors, and lightweight-controlled thyristors. The working condition from the thyristor is the fact that whenever a forward voltage is applied, the gate needs to have a trigger current.

Characteristics of thyristor

1. Forward blocking

As shown in Figure a above, when an ahead voltage can be used involving the anode and cathode (the anode is linked to the favorable pole from the power supply, and also the cathode is connected to the negative pole from the power supply). But no forward voltage is applied for the control pole (i.e., K is disconnected), and also the indicator light will not illuminate. This implies that the thyristor is not conducting and it has forward blocking capability.

2. Controllable conduction

As shown in Figure b above, when K is closed, and a forward voltage is applied for the control electrode (known as a trigger, and also the applied voltage is called trigger voltage), the indicator light switches on. Because of this the transistor can control conduction.

3. Continuous conduction

As shown in Figure c above, following the thyristor is switched on, whether or not the voltage on the control electrode is removed (which is, K is switched on again), the indicator light still glows. This implies that the thyristor can still conduct. At the moment, to be able to cut off the conductive thyristor, the power supply Ea should be cut off or reversed.

4. Reverse blocking

As shown in Figure d above, although a forward voltage is applied for the control electrode, a reverse voltage is applied involving the anode and cathode, and also the indicator light will not illuminate at the moment. This implies that the thyristor is not conducting and may reverse blocking.

5. In summary

1) Once the thyristor is put through a reverse anode voltage, the thyristor is within a reverse blocking state no matter what voltage the gate is put through.

2) Once the thyristor is put through a forward anode voltage, the thyristor is only going to conduct when the gate is put through a forward voltage. At the moment, the thyristor is in the forward conduction state, which is the thyristor characteristic, which is, the controllable characteristic.

3) Once the thyristor is switched on, as long as there exists a specific forward anode voltage, the thyristor will stay switched on no matter the gate voltage. That is, following the thyristor is switched on, the gate will lose its function. The gate only works as a trigger.

4) Once the thyristor is on, and also the primary circuit voltage (or current) decreases to seal to zero, the thyristor turns off.

5) The disorder for your thyristor to conduct is the fact that a forward voltage needs to be applied involving the anode and also the cathode, as well as an appropriate forward voltage ought to be applied involving the gate and also the cathode. To turn off a conducting thyristor, the forward voltage involving the anode and cathode should be cut off, or even the voltage should be reversed.

Working principle of thyristor

A thyristor is essentially a distinctive triode composed of three PN junctions. It can be equivalently thought to be composed of a PNP transistor (BG2) as well as an NPN transistor (BG1).

1. In case a forward voltage is applied involving the anode and cathode from the thyristor without applying a forward voltage for the control electrode, although both BG1 and BG2 have forward voltage applied, the thyristor continues to be switched off because BG1 has no base current. In case a forward voltage is applied for the control electrode at the moment, BG1 is triggered to generate basics current Ig. BG1 amplifies this current, and a ß1Ig current is obtained in its collector. This current is precisely the base current of BG2. After amplification by BG2, a ß1ß2Ig current will likely be brought in the collector of BG2. This current is sent to BG1 for amplification and after that sent to BG2 for amplification again. Such repeated amplification forms a vital positive feedback, causing both BG1 and BG2 to get in a saturated conduction state quickly. A large current appears in the emitters of the two transistors, which is, the anode and cathode from the thyristor (how big the current is actually determined by how big the stress and how big Ea), and so the thyristor is completely switched on. This conduction process is finished in an exceedingly short period of time.
2. After the thyristor is switched on, its conductive state will likely be maintained from the positive feedback effect from the tube itself. Even if the forward voltage from the control electrode disappears, it is still in the conductive state. Therefore, the purpose of the control electrode is only to trigger the thyristor to turn on. When the thyristor is switched on, the control electrode loses its function.
3. The only way to switch off the turned-on thyristor would be to lessen the anode current that it is insufficient to maintain the positive feedback process. How you can lessen the anode current would be to cut off the forward power supply Ea or reverse the link of Ea. The minimum anode current required to maintain the thyristor in the conducting state is called the holding current from the thyristor. Therefore, as it happens, as long as the anode current is under the holding current, the thyristor may be switched off.

What is the difference between a transistor and a thyristor?

Structure

Transistors usually contain a PNP or NPN structure composed of three semiconductor materials.

The thyristor is composed of four PNPN structures of semiconductor materials, including anode, cathode, and control electrode.

Working conditions:

The work of any transistor relies on electrical signals to control its opening and closing, allowing fast switching operations.

The thyristor needs a forward voltage and a trigger current in the gate to turn on or off.

Application areas

Transistors are commonly used in amplification, switches, oscillators, along with other aspects of electronic circuits.

Thyristors are mainly utilized in electronic circuits such as controlled rectification, AC voltage regulation, contactless electronic switches, inverters, and frequency conversions.

Way of working

The transistor controls the collector current by holding the base current to achieve current amplification.

The thyristor is switched on or off by manipulating the trigger voltage from the control electrode to comprehend the switching function.

Circuit parameters

The circuit parameters of thyristors are based on stability and reliability and in most cases have higher turn-off voltage and larger on-current.

To sum up, although transistors and thyristors may be used in similar applications in some instances, because of their different structures and working principles, they may have noticeable differences in performance and make use of occasions.

Application scope of thyristor

• In power electronic equipment, thyristors may be used in frequency converters, motor controllers, welding machines, power supplies, etc.
• Inside the lighting field, thyristors may be used in dimmers and lightweight control devices.
• In induction cookers and electric water heaters, thyristors may be used to control the current flow for the heating element.
• In electric vehicles, transistors may be used in motor controllers.

Supplier

PDDN Photoelectron Technology Co., Ltd is a wonderful thyristor supplier. It is one from the leading enterprises in the Home Accessory & Solar Power System, which can be fully working in the development of power industry, intelligent operation and maintenance control over power plants, solar power panel and related solar products manufacturing.

It accepts payment via Charge Card, T/T, West Union and Paypal. PDDN will ship the goods to customers overseas through FedEx, DHL, by air, or by sea. If you are looking for high-quality thyristor, please feel free to contact us and send an inquiry.